1. Field of the Invention
The present invention relates to a lens actuating apparatus. In particular, this invention relates to a lens actuating apparatus that is applied to a mini image-capturing module for actuating the lens.
2. Description of the Related Art
Recently, the image-capturing module becomes a popular module for hand-held devices, such as cell phones, Personal Digital Assistants (PDAs), etc. As the hand-held devices have a trend of having high quality functions and being smaller, the image-capturing module has to meet the requirements of having high image quality and being miniaturized. For enhancing the image quality of the image-capturing module, the first method is to increase the image pixels. The number of image pixels has been increased from three hundred thousands pixels, to one million pixels, two million pixels, three million pixels, four million pixels, and five million pixels. The second method is to improve the definition of the captured-image. The function of the image-capturing module of the hand-held device has been improved from constant focal distance image-capturing to automated optical focusing and zooming.
The operation principle of the automated optical focusing is to properly move the lens in the image-capturing module according to the distance of the target object so that the optical image of the target object is exactly focused on the image sensor to generate a clear image. The lens in the image-capturing module is actuated by a stepping motor, a piezoelectricity actuator, or a voice coil motor, etc.
The voice coil motor is to place a coil in a magnetic path of a permanent magnet. According to Fleming's left hand rule, the coil reacts with the permanent magnet to generate a pushing force when the coil is conducted, and the carrying base connected with the permanent magnet is moved. Thereby, the lens set fastened on the carrying base is moved. However, the actuating force from the voice coil motor has to be balanced with a recovering force to make the lens positioning on the target position. Therefore, a flexible plate is added to the voice coil motor to provide the recovering force. Then, by adjusting the current flowing through the coil, the optical zooming and focusing functions are achieved.
Taiwan patent M285846 (application number: 094217663) discloses a flexible plate with a voice coil motor. It locks flexible plate with the lens frame and the outer frame of the voice coil motor. By utilizing the flexible force of the flexible plate, the recovering force is obtained. However, the design of the flexible plate is similar to the design of an inner circular plate connected with an outer circular plate into one piece. The dimensions of the flexible plate cannot be reduced to meet the requirements of the image-capturing module being miniaturized.
Japanese patent 2005-128392 discloses a lens actuating apparatus. The lens actuating apparatus includes a front flexible plate and a rear flexible plate. By utilizing the front flexible plate and the rear flexible plate, the recovering force is obtained. However, the design of the lens actuating apparatus is also similar to the design of an inner circular plate connected with an outer circular plate into one piece. The drawback is the same as the above.
Furthermore, Japanese patent 2002-365514 discloses a lens actuating apparatus. The lens actuating apparatus also includes a front flexible plate and a rear flexible plate. The front flexible plate and the rear flexible plate respectively are composed of a semi-circular inner portion and a semi-circular outer portion. The design of the lens actuating apparatus is the same as to the design of an inner circular plate connected with an outer circular plate. It also has the same drawback. The design of the other elements is restricted by the dimensions of the lens actuating apparatus, and the image-capturing module cannot be miniaturized.